Hw and methods for improving safety protocol in wireless chargers

ABSTRACT

An over-voltage protection circuit and methods of operation are provided. In one embodiment, a method includes monitoring a voltage at an output of a rectifier, a voltage at an output of a voltage regulator, or a combination thereof. The method further includes determining the over-voltage condition based on the monitoring; and in response to determining the over-voltage condition, regulating the voltage at the output of the rectifier in accordance with a voltage difference between the voltage at the output of the rectifier and the voltage at the output of the voltage regulator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 17/374,840, filed on Jul. 13, 2021, which is a divisionalapplication of U.S. application Ser. No. 16/413,283, filed on May 15,2019, now issued as U.S. Pat. No. 11,095,146, which applications arehereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to hardware (HW), and inparticular embodiments, to an over-voltage protection circuit in awireless power system.

BACKGROUND

Generally, a wireless power system uses mutual coupling to transferpower from a transmitting device to a receiving device. Myriad of causescan trigger the transmitting device to provide a voltage exceeding theoperating capabilities of the various components of the receivingdevice. The excess power can cause hazardous conditions to the user, thereceiving device, and the transmitting device.

Existing methods and systems use clamping of the AC voltage at thereceiver side or de-tuning of the system impedance to counteract theexcess voltage condition. As an example, a Zener clamping circuit isused to clamp the incoming AC voltage at the receiver side. As anotherexample, de-tuning the receiving circuit may reduce the coupling factorbetween the primary winding and the secondary winding of the transformerand reduce the incoming power. Each solution can provide limitedprotection. However, the system remains susceptible to large amounts ofincoming power.

Another method to counteract the excess power condition is hardover-voltage protection (HOVP). In hard over-voltage protection, whenincoming voltage exceeds a threshold, the protection is triggered andthe loading elements are shorted to ground. This solutiondisadvantageously causes the excess power to be dissipated solely inlocalized elements. Generally speaking, an excess of incoming powershould be spread over several elements to avoid overstressing a singleelement. Additionally, the solution may cause in-band communicationissues between the receiving device and the transmitting device, whichmay impact the response time for the transmitting device to reduce theexcess power.

Thus, a need exists for an improved system and method to overcome theseand other limitations in the existing solutions to counteractover-voltage conditions in wireless power systems.

SUMMARY

Technical advantages are generally achieved by embodiments of thisdisclosure, which describe an over-voltage protection circuit in awireless power system.

A first aspect relates to an over-voltage protection circuit, theover-voltage protection circuit includes a first and second differentialamplifier, a comparator, a switch, and a regulating circuit. A firstinput of the first differential amplifier is coupled to an output of arectifier and a second input of the first differential amplifier iscoupled to an output of a voltage regulator. A first input of the seconddifferential amplifier is coupled to an output of the first differentialamplifier and a second input of the second differential amplifier iscoupled to a first reference voltage. A first input of the comparator iscoupled to the output of the first differential amplifier and a secondinput of the comparator is coupled to a second reference voltage. Aninput of the switch is coupled to the output of the second differentialamplifier and a control terminal of the switch is coupled to an outputof the comparator. An input of the regulating circuit is coupled to theoutput of the rectifier, a control terminal of the regulating circuit iscoupled to the output of the switch, and an output of the regulatingcircuit is coupled to reference ground.

In a first implementation form of the over-voltage protection circuitaccording to the first aspect, the first differential amplifier isconfigured to provide an output voltage corresponding to an amplifieddifference between a voltage at the output of the rectifier and avoltage at the output of the voltage regulator. The output voltage ofthe first differential amplifier is provided to each of the comparatorand the second differential amplifier.

In a second implementation form of the over-voltage protection circuitaccording to the first aspect as such or any preceding implementationform of the first aspect, the second differential amplifier isconfigured to provide a control voltage to the control terminal of theregulating circuit. A value of the control voltage corresponds to anamplified voltage difference between a voltage at the output of therectifier and a voltage at the output of the voltage regulator inreference to the first reference voltage.

In a third implementation form of the over-voltage protection circuitaccording to the first aspect as such or any preceding implementationform of the first aspect, the comparator is configured to provide acontrol signal to the switch. A value of the control signal correspondsto an amplified voltage difference between a voltage at the output ofthe rectifier and a voltage at the output of the voltage regulator inreference to the second reference voltage.

In a fourth implementation form of the over-voltage protection circuitaccording to the first aspect as such or any preceding implementationform of the first aspect, the switch is activated in response to avoltage difference between a voltage at the output of the rectifier anda voltage at the output of the voltage regulator exceeding a firstthreshold, the voltage at the output of the rectifier exceeding a secondthreshold, the voltage the output of the voltage regulator exceeding athird threshold, or a combination thereof.

In a fifth implementation form of the over-voltage protection circuitaccording to the first aspect as such or any preceding implementationform of the first aspect, the regulating circuit is configured toregulate a voltage at the output of the rectifier in accordance with acontrol voltage provided by the second differential amplifier.

In a sixth implementation form of the over-voltage protection circuitaccording to the first aspect as such or any preceding implementationform of the first aspect, the regulating circuit includes an activedevice and a dissipating element.

A second aspect relates to device that includes a rectifier, a voltageregulator, a monitoring circuit, and a regulating circuit. The rectifieris configured to receive an alternating current (AC) voltage and outputa direct current (DC) voltage. The voltage regulator is configured toreceive the DC voltage and output a regulated DC voltage. The monitoringcircuit includes a first differential amplifier, a second differentialamplifier, a comparator, and a switch. The monitoring circuit isconfigured to monitor the DC voltage, the regulated DC voltage, adifference between the DC voltage and the regulated DC voltage, or acombination thereof. The regulating circuit configured to regulate theDC voltage in response to the monitoring circuit determining that the ACvoltage exceeds a steady-state operating condition.

In a first implementation form of the device according to the secondaspect, the monitoring circuit further includes a multiplexer, a secondcomparator, and a third comparator. The regulating circuit is activatedbased on a combinational logic of the value of the DC voltage, theregulated DC voltage, and a voltage difference between the DC voltageand the regulated DC voltage.

In a second implementation form of the device according to the secondaspect as such or any preceding implementation form of the secondaspect, the device further includes a microcontroller configured tocommunicate an End Power Transfer (EPT) request to stop the AC voltagein response to the AC voltage exceeding the steady-state operatingcondition.

In a third implementation form of the device according to the secondaspect as such or any preceding implementation form of the secondaspect, the microcontroller is configured to communicate the EPT requestafter a delay period is elapsed from a time that the regulating circuitbegins to regulate the DC voltage.

In a fourth implementation form of the device according to the secondaspect as such or any preceding implementation form of the secondaspect, the communicating the EPT request is communicated using anin-band communication path.

In a fifth implementation form of the device according to the secondaspect as such or any preceding implementation form of the secondaspect, the regulating circuit is further configured to stop regulatingthe DC voltage after an elapsing of a programmable time period at whichtime the rectifier is configured in a hard over-voltage protection modeto stop receiving the AC voltage.

In a sixth implementation form of the device according to the secondaspect as such or any preceding implementation form of the secondaspect, the device further includes a load configured to receive theregulated DC voltage.

A third aspect relates to a method for regulating an over-voltagecondition in a wireless power system, the method includes monitoring avoltage at an output of a rectifier, a voltage at an output of a voltageregulator, or a combination thereof. The method further includesdetermining the over-voltage condition based on the monitoring; and inresponse to determining the over-voltage condition, regulating thevoltage at the output of the rectifier in accordance with a voltagedifference between the voltage at the output of the rectifier and thevoltage at the output of the voltage regulator.

In a first implementation form of the method according to the thirdaspect, the method further includes communicating an End Power Transfer(EPT) request using an in-band communication path after determining theover-voltage condition.

In a second implementation form of the method according to the thirdaspect as such or any preceding implementation form of the third aspect,the communicating the EPT request is delayed for a set length of timeafter determining the over-voltage condition.

In a third implementation form of the method according to the thirdaspect as such or any preceding implementation form of the third aspect,monitoring the voltages includes continuously comparing one or more ofthe voltage at the output of the rectifier, the voltage at the output ofthe voltage regulator, or a voltage difference between the voltage atthe output of the rectifier and the voltage at the output of the voltageregulator to a respective reference voltage.

In a fourth implementation form of the method according to the thirdaspect as such or any preceding implementation form of the third aspect,each respective reference voltage is a programmable value.

In a fifth implementation form of the method according to the thirdaspect as such or any preceding implementation form of the third aspect,determining the over-voltage condition based on the monitoring includesdetermining that one or more combinational logic of the output of thecomparing satisfies the over-voltage condition.

Embodiments can be implemented in hardware, software, or in anycombination thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a wireless power system;

FIG. 2 is a schematic diagram of an embodiment wireless power systemhaving a regulation loop circuit;

FIG. 3 is a schematic diagram of another embodiment wireless powersystem having a regulation loop circuit;

FIG. 4 is a schematic of an embodiment regulating circuit for a wirelesspower system;

FIGS. 5A-C are plots of embodiment operational timing diagrams;

FIG. 6 is a schematic diagram of an embodiment wireless power systemhaving a current sensing element;

FIG. 7A is a schematic diagram of a receiving device configured withZener diodes in a clamping circuit;

FIG. 7B is a schematic diagram of a receiving device configured with ade-tuning circuit;

FIG. 7C is a schematic diagram of a receiving device configured withhard over-voltage protection; and

FIG. 8 is a flowchart of an embodiment method for monitoring andregulating voltages in a wireless power system to address anover-voltage condition.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

This disclosure provides many applicable inventive concepts that can beembodied in a wide variety of specific contexts. The specificembodiments are merely illustrative of specific configurations and donot limit the scope of the claimed embodiments. Features from differentembodiments may be combined to form further embodiments unless notedotherwise.

Variations or modifications described with respect to one of theembodiments may also be applicable to other embodiments. Further, itshould be understood that various changes, substitutions, andalterations can be made herein without departing from the spirit andscope of this disclosure as defined by the appended claims.

While the inventive aspects are described primarily in the context of awireless power system and inductive coupling, it should also beappreciated that these inventive aspects may also be applicable to anytype of wireless energy transfer. For example, the embodiment methodsand systems described in this disclosure can be similarly applied tocapacitive coupling. Furthermore, the wireless power system may operateusing resonant or non-resonant coupling.

In a typical wireless power system, mutual coupling is used towirelessly transfer power from a transmitting device to one or morereceiving devices. For instance, a transmitting device generates analternating current (AC), using a power source. An alternating currentat a first set of windings, or coils, of the transmitting devicegenerates an alternating current at a second set of windings of thereceiving device, using mutual inductance. The receiving device, using arectifier, converts the alternating current at the second windings to adirect current (DC) voltage. The DC voltage may then be stored in abattery or consumed at a load of the receiving device.

A potential safety issue may arise if the received power, at thereceiving device, exceeds the power need of the receiving devicecomponent(s) (e.g., receiving elements, load elements, etc.). This maylead to situations in which the receiving elements exceed theiroperating limits.

It is typical for the transmitting device to generate more power thanmay be required by the receiving device. For instance, the transmittingdevice may be used to wirelessly transfer power to more than onereceiving device. In this example, the transmitting device may generatesufficient power to support both receiving devices. As another example,the transmitting device may increase the power at the transmitting endto compensate for losses between the transmitting and receiving devicesdue to, for example, a mismatch between the two devices.

For various reasons, the receiving device may receive an excess ofincoming power that exceeds the operating limits of the receivingdevice. For instance, a load element at the receiving device may bedisconnected and the event may not be properly communicated to thetransmitting device in a request to reduce the power level. Or thereceiving device may be slightly repositioned in reference to thetransmitting device, which may cause a change in an impedance at eachcoil. It is possible that the coupling between the two devices is nowimproved and the receiving device suddenly receives a large amount ofpower. As another example, a defect at the transmitting device may leadto excess power to be received by the receiving device.

Regardless of the cause, an excess of incoming power at the receivingdevice may lead to a presence of an excess voltage (i.e., over-voltage)across, or an excess current (i.e., over-current) through, the receivingand loading elements of the receiving device. The excess of incomingpower may instantly, or gradually, damage the components of thereceiving device, or even the components of the transmitting device,which may be additionally harmful and hazardous to the end-user.Accordingly, system and methods to ensure the safe operation of thewireless power transfer are desired.

Amplitude shift keying (ASK) modulation is a form of modulation that canbe used for communication between the transmitting device and thereceiving device. In ASK modulation, the carrier frequency signal ismultiplied by a binary digital to form a variable amplitude signal andinformation is communicated in the form of the carrier's amplitude. Thereceiving device uses backscatter modulation, by modulating the powerdrawn from the transmitting device, to communicate with the transmittingdevice. In an exemplary communication protocol, the ASK modulationallows the receiving device to communicate with the transmitting device.

In previous solutions, the ASK modulation signal becomes erratic and thesignal communicated from the receiving device to the transmittingdevice, for example, the end power transfer (EPT) request, becomescorrupted. As a result, the transmitting device may not be able toproperly receive the communication from the receiving device and the EPTrequest may be ignored. This in turn may cause continued damage to oneor both of the devices.

Embodiments of this disclosure provide a system and method to monitor anover-voltage condition in a receiving device of the wireless powersystem. In various embodiments, a monitoring circuit determines theover-voltage condition at the output of a rectifier and/or at the outputof a voltage regulator. Each voltage may be compared to a thresholdvoltage to determine the over-voltage condition. In some embodiments,the monitoring circuit is used to determine whether the voltage at theoutput of the rectifier exceeds the voltage at the output of theregulator by a threshold voltage. In some embodiments, the monitoringcircuit may use a combinational logic, based on direct or differentialmonitoring of the various voltages, to determine the over-voltagecondition.

In response to determining that an over-voltage condition has occurred,a regulating circuit is used to regulate the voltage at the output ofthe rectifier. In the event of an over-voltage condition, the monitoringcircuit provides a control voltage to the regulating circuit. Theregulating circuit includes an active device coupled to a dissipatingelement. The input of the active device is coupled to a node sharedbetween the output of the rectifier and the input of the voltageregulator. The output of the active device is coupled to a dissipatingelement connected to the reference ground. The conductivity of theactive device is controlled by the value of the control voltage. As theconductivity of the active device changes, the amount that thedissipating element dissipates varies. The control voltage is set suchthe dissipating element only dissipates the amount needed to regulatethe output of the rectifier to the steady-state operational condition.Advantageously, the excess power is spread at the load and theregulating circuit, which minimizes damage to each device.

Aspects of this disclosure provide a regulated voltage in the event ofan over-voltage condition, permitting the receiving device tocommunicate the abnormal condition to the transmitting device using, forexample, ASK modulation. The monitoring circuit and the regulatingcircuit form a regulation loop circuit that ensures proper in-bandcommunication from the receiving device to and from the transmittingdevice. In some embodiments, the regulation loop circuit conditions thevoltage at the input of the voltage regulator to a stable value for aperiod of time such that the receiving device can communicate a requestto the transmitting device for a reduction in the level of the powertransference. Thus, the various receiving and loading elements of thereceiving device remain properly biased to allow the receiving device anopportunity to communicate with the transmitting device.

In some embodiments, the receiving device may send an end power transfer(EPT) request to the transmitting device after an elapsing of a specificperiod of time from the activation of the regulating circuit. Thisadvantageously provides the wireless power system a period of time toignore any short surges of incoming power from the transmitting deviceto the receiving device, and to ignore any faulty information whichwould result, for example, from noise originating from the detectionsystem (e.g., de-bouncing system). Thus, providing a smooth reactionresponse to an excess input power condition at the receiving device.These and other details are discussed in greater detail below.

FIG. 1 illustrates a schematic diagram of a wireless power system 100.The wireless power system 100 includes a transmitting device 110 and areceiving device 120. The wireless power system 100 is used towirelessly transfer power 140 from the transmitting device 110 to thereceiving device 120. The transmitting device 110 may be a base station,such as a wireless charger, which provides inductive power. Thereceiving device 120 may be a mobile device, such as a personal computer(PC), a tablet, a cellular phone, a wearable communications device(e.g., a smartwatch, etc.), a toothbrush, an internet of things (IOTs)device, or others. The receiving device 120 consumes inductive power.

The transmitting device 110 may have a flat surface on which thereceiving device 120 may be placed. The receiving device 120 may useguided positioning or free positioning to properly position thereceiving device 120 with respect to the transmitting device 110.

The transmitting device 110 includes a power source 112, a supply-sidecapacitor 114, and first windings 116. The receiving device 120 includessecond windings 122, a resonant capacitor 124, a rectifier 126, a shuntcapacitor 128, a voltage regulator 130, and a load 132.

The power source 112 is any device that generates alternating current(AC) power supplied to the first windings 116. Each of the firstwindings 116 and second windings 122 may be a loop antenna or a magneticantenna. The windings may include a physical core (e.g., ferrite core)or an air core. The windings may be implemented as an antenna strip orusing a Litz wire. The resonant frequency of the windings is based onthe shape and size of the looping wire or coil. In some embodiments,additional capacitance and inductance may be added to each winding tocreate a resonant structure at the desired resonant operating frequency.

The rectifier 126 is a device that converts an alternating current (AC)voltage to a direct current (DC) voltage. The rectifier 126 may be anytype of rectifier, such as a low-impedance synchronous rectifier havingfull-wave or half-wave rectification. The rectifier 126 shown in FIG. 1is a bridge rectifier, however, other types of rectifiers may also becontemplated.

The shunt capacitor 128 may be referred to as a smoothing or a reservoircapacitor. The shunt capacitor 128 is used to decrease any ripple at theinput of the voltage regulator 130 from the rectifier 126. A terminal ofthe shunt capacitor 128 is shared with the output terminal of therectifier 126 and an input terminal of the voltage regulator 130 at theV_(RECT) node 220. The second terminal of the shunt capacitor 128 isconnected to the reference voltage V_(REF) at the V_(REF) node 160.Additional filtering components may be contemplated.

The voltage regulator 130 is a device that maintains a constant outputvoltage for the load 132. The voltage regulator 130 receives an inputvoltage from the rectifier 126. The voltage regulator 130 may be anytype of voltage regulator, such as a linear regulator (e.g., lowdrop-out (LDO) linear regulator).

In some embodiments, the rectifier 126 and voltage regulator 130 may bepart of a switched-mode power supply (SMPS) circuit.

The transferred power is received at the load 132. The load 132 may be acharge storage device, such as a battery. For instance, the load 132 maybe a battery of a cellular phone. The transmitting device may be acharging pad and the cellular phone may be placed on the charging pad.The charging pad transfers wireless power to the battery of the cellularphone without the need for interconnecting cables between the twodevices.

The power source 112 generates an alternating current (AC) at the firstwindings 116, which induces a magnetic field at the second windings 122,typically at a specified distance. The induced magnetic field in turninduces an alternating current at the second windings 122 through mutualcoupling. The rectifier 126 converts the AC voltage at the secondwindings 122 to a direct current (DC) voltage. The voltage regulator 130converts the DC voltage to match a desired DC voltage for the load 132.

The receiving device 120 can communicate with the transmitting device110, for example, to properly adjust the power received at the receivingdevice 120. A number of interface standards have been developed with thegoal of standardizing wireless power transfer and related functions. Forinstance, Qi, which is promoted by the Wireless Power Consortium (WPC),and Rezence, which is promoted by the AirFuel Alliance are two competingstandards that define interface standards for wireless power transfer.These and other similar types of protocols may be used to define thecommunication interface for adjusting the power supplied by thetransmitting device 110 and demanded by the receiving device 120. Forinstance, the receiving device 120 may request, from the transmittingdevice 110, a change (e.g., an increase or decrease) in the amount ofpower that is being received. The receiving device 120 may communicatewith the transmitting device using an in-band (e.g., Qi) or anout-of-band (e.g., AirFuel Alliance) communication path. In-bandcommunication refers to signaling over the power path and/or at the samefrequency as the power transfer. Out-of-band communication path refersto signaling over a different channel and/or at a different frequencythan the power transfer.

The transmitting device 110 may change the amount of power that is beinggenerated by the power source 112 as a result of an instruction receivedin a signal, or packet, 150 from the receiving device 120. Thus, afeedback loop system may be utilized to adjust the amount of powertransferred from the transmitting device 110 to the receiving device120. However, when the receiving device 120 becomes exposed to anexcessive amount of power at the second windings 122, a period of timemay elapse before the transmitting device 110 receives the instructionsand acts to reduce the power received at the receiving device 120.Additionally, the transmitting device 110 may not properly receive anupdated request to reduce the power level due to, for example, a corruptsignal exchange.

As an example, the transmitting device 110 may be capable of providingup to 30 Volts (V) at the rectifier 126. The receiving device 120 may beoperating stably and receiving more than 10 V at the rectifier 126.Imagine that an end-user quickly substitutes the receiving device 120with a new receiving device, and where the new receiving device does nothave an initial load. In this scenario, the transmitting device 110 isstill transmitting with the assumption that the device receiving thepower is the old receiving device 120. Immediately after thistransition, the new receiving device, without the initial load, will beexposed at a high voltage at its corresponding rectifier. The newreceiving device, to protect itself against over-voltage, may clamp thishigh voltage. As a result of the clamping, packets sent from the newreceiving device may now be corrupted. A request to reduce the power tothe transmitting device 110 using the corrupt packets may not beproperly received at the transmitting device 110. Accordingly, the newreceiving device may be exposed to a large amount of power for anextended period of time, which may result in damage to variouscomponents in the new receiving device.

As another example, the receiving device 120, with established receivingpower transmitted from the transmitting device 110, may replace a secondreceiving device, with higher established receiving power previouslyfrom a second transmitter in a second wireless power system. In thisexample, the receiving device 120 would be exposed to a higher power inthe second wireless power system.

FIG. 2 is a schematic diagram of an embodiment wireless power system 200having a regulation loop circuit 240. The wireless power system 200 isused to provide a regulated voltage from the transmitting device 110 tothe load 132. The regulation loop circuit 240 provides protectionagainst over-voltage conditions at the load or receiving elements of thereceiving device 120. Moreover, the regulation loop circuit 240 allowsproper ASK modulation signaling to communicate the over-voltagecondition from the receiving device 120 to the transmitting device 110.

The receiving device 120 in the wireless power system 200, in additionto the components previously discussed in FIG. 1 , includes a firstdifferential amplifier 202, a second differential amplifier 204, acomparator 206, a switch 208, a regulating circuit 210, and amicrocontroller 212, which may (or may not) be arranged as shown in FIG.2 . The transmitting device 110 in the wireless power system 200, inaddition to the components previously discussed in FIG. 1 , includes amicrocontroller 214, which may (or may not) be arranged as shown in FIG.2 . The receiving device 120 and the transmitting device 110 may includeadditional components not depicted in FIG. 2 , such as long-term storage(e.g., non-volatile memory, etc.), a non-transitory computer-readablemedium, one or more antenna elements, filter circuits, and impedancematching circuits.

The microcontroller 212 is coupled to the various components of thereceiving device 120. The microcontroller 214 is coupled to the variouscomponents of the transmitting device 110. The microcontrollers 212 and214 may be a part of a communications and control unit of each device.Microcontrollers 212 and 214 regulate the transferred power from thetransmitting device 110 to the level requested by the receiving device120. Communication between the microcontrollers 212 and 214 may beunidirectional or bi-directional. Furthermore, the communication may bein-band or out-of-band to the wireless power transfer frequency. Invarious embodiments, the communication may be in accordance with astandard protocol interface, such as that promoted by the wireless powerconsortium (i.e., Qi).

The output of the rectifier 126, the input of the voltage regulator 130,and a first terminal of the shunt capacitor 128 share the rectifiedvoltage (V_(RECT)) node 220. The output of the voltage regulator 130 andthe input of the load 132 share the regulated output voltage (V_(OUT))node 230. The voltage at the V_(RECT) node 220 is referred to asV_(RECT). The voltage at the V_(OUT) node 230 is referred to as V_(OUT).

Each of the differential amplifiers 202 and 204 receive a pair of inputvoltages at a corresponding pair of input terminals. Each differentialamplifier provides an amplified difference of the two input voltages atits output. In some embodiments, one or both of the differentialamplifiers 202 and 204 may be an operational amplifier (op-amp)configured for providing gain.

For example, the first differential amplifier 202 may be an op-ampconfigured for providing unity gain, while the second differentialamplifier 204 may be another op-amp configured for providing a high gain(e.g., >20 decibels (dB)). This configuration advantageously ensuresthat the regulation loop circuit 240 has enough open loop gain forproper and reliable operation. The regulation loop circuit 240 isdiscussed in further detail below.

A first (i.e., non-inverting) input of the first differential amplifier202 is coupled to the V_(RECT) node 220. A second (i.e., inverting)input of the first differential amplifier 202 is coupled to the V_(OUT)node 230. It should be noted that in some embodiments the V_(RECT) node220 may be coupled to the inverting input of the first differentialamplifier 202 and the V_(OUT) node 230 may be coupled to thenon-inverting input of the first differential amplifier 202. It istypical for a person of ordinary skill in the art (POSITA) to configurethe individual gains such that the overall feedback is a negativefeedback.

An output of the first differential amplifier 202 provides an amplifieddifference between the voltages V_(RECT) and V_(OUT). In someembodiments, the output of the first differential amplifier 202 may be anon-amplified (i.e., gain of 0 dB) difference between the voltagesV_(RECT) and V_(OUT).

A first (i.e., non-inverting) input of the second differential amplifier204 is coupled to the output of the first differential amplifier 202. Asecond (i.e., inverting) input of the second differential amplifier 204is coupled to a first reference voltage (V_(REF1)). Similar to the caseof the first differential amplifier 202, the input signals to theinverting and non-inverting inputs of the second differential amplifier204 may be swapped while maintaining overall loop stability.

An output of the second differential amplifier 204 provides an amplifieddifference between the output voltage of the first differentialamplifier 202 and the voltage V_(REF1). In some embodiments, the outputof the second differential amplifier 204 may be a non-amplified (i.e.,gain of 0 dB) difference between the output voltage of the firstdifferential amplifier 202 and the voltage V_(REF1). The output of thesecond differential amplifier 204 may correspond to one or more of thegain of the first differential amplifier 202, the gain of the seconddifferential amplifier 204, and the value of V_(REF1). In other words,the output voltage of the second differential amplifier 204 isconfigurable using several controllable parameters. Generally speaking,the overall regulation loop gain is configured, such that by thedistribution of the gain between the first differential amplifier 202,the second differential amplifier 204—and to an extent—the regulatingcircuit 210, the overall regulation loop is provided sufficient gain toensure proper regulation and stability.

The comparator 206 receives a pair of input voltages (or currents) andprovides a digitized output (i.e., “0” or “1”), at a specific voltage,based on a comparison of the value at the two inputs. For example, acomparator may have a positive side input and a negative side input. Inthis example, the output voltage may indicate a digital representationof “1” if the voltage at the positive side is greater than the voltageat the negative side and indicate a digital representation of “0” if thevoltage at the negative side is greater than the voltage at the positiveside, or vice-versa.

A first (i.e., positive-side) input of the comparator 206 is coupled tothe output of the first differential amplifier 202. A second (i.e.,negative-side) input of the comparator 206 is coupled to a secondreference voltage (V_(REF2)). It should be noted in some embodiments,the input voltages at the positive side and the negative side of thecomparator 206 may be swapped.

Switch 208 can be, but is not limited to, a field-effect transistor(FET) or a bipolar junction transistor (BJT). A FET can be ametal-oxide-semiconductor FET (MOSFET), a junction FET (JFET), aninsulated-gate bipolar transistor (IGBT), or any other semiconductordevice used as a switch. The FET device may be a negative-type or apositive-type FET. For instance, the switch 208 may be an n-MOSFET,p-MOSFET, or the like.

An input of switch 208 is coupled to the output of the seconddifferential amplifier 204. Switch 208 includes a control terminal(e.g., gate terminal in a FET) that receives a control voltage from anoutput of the comparator 206. An output of switch 208 is coupled to theregulating circuit 210.

Switch 208 operates in either open or closed mode. In the close mode,switch 208 provides a voltage (V_(CONT)), at the V_(CONT) node 250, fromthe second differential amplifier 204 to the regulating circuit 210. Inthe open mode, switch 208 blocks the voltage V_(CONT) from the seconddifferential amplifier 204 to be received at the regulating circuit 210.In an embodiment, switch 208 may operate as normally open. In anembodiment, V_(CONT) may have a value from about −0.3 V to about 27 V.

The regulating circuit 210 receives the voltage V_(CONT) from switch208. The regulating circuit 210 regulates the voltage at the V_(RECT)node 220 based on the value of the voltage V_(CONT). In an embodiment,excess power is dissipated from the V_(RECT) node 220 through theregulating circuit 210. In one embodiment, the regulating circuit 210may be a discrete component. In some embodiments, the regulating circuit210 may include at least one active component. In some embodiments, theregulating circuit 210, in addition to the at least one activecomponent, may include one or more active or passive components. Theseand other details of the regulating circuit 210 are discussed furtherbelow in reference to FIG. 4 .

The differential amplifiers 202 and 204, the comparator 206, the switch208, and the regulating circuit 210 form a regulation loop circuit 240.The regulation loop circuit 240, in response to determining that thevalue of V_(RECT) exceeds an operational limit of the receiving device120, utilizes the regulating circuit 210 to dissipate the excess powerfrom the V_(RECT) node 220. The regulation loop circuit 240 includesa 1) monitoring circuit, comprising the differential amplifiers 202 and204, the comparator 206, and the switch 208, and 2) the regulatingcircuit 210.

In other words, the regulation loop circuit 240 is used to detectwhether or not V_(RECT), which is the input voltage to the voltageregulator 130, is causing the voltage across the voltage regulator 130to exceed a threshold limit set for the system. In response todetermining that this threshold has been exceeded, the regulatingcircuit 210 is activated. The controlled activation of the regulatingcircuit 210 allows the reduction of V_(RECT) to a value at which thevoltage regulator 130 and load 132 can remain in the proper operationalvoltage.

In an original steady-state operation, or proper operational mode (i.e.,when V_(RECT) is within normal operating conditions), the voltageregulator 130 provides a properly regulated voltage at the V_(OUT) node230 to load 132. For example, the value of V_(RECT) may be about 20.5 Vwhile the value of V_(OUT) may be about 20 V. In an excess of incomingpower condition, V_(RECT) increases, and the regulating circuit 210 inthe regulation loop circuit 240 is activated. As a result, V_(RECT) isclamped at about 22 V. The wireless power system 200 is now operating ina new steady-state operational mode and the voltage regulator 130continues to provide a properly regulated voltage V_(OUT). It is notedthat the regulating circuit 210 absorbs the excess of power.

The value of the V_(REF2) voltage is set such that the switch 208remains open as long as the amplified difference between V_(RECT) andV_(OUT) is less than an operational threshold of the receiving device120. If the amplified difference between V_(RECT) and V_(OUT) exceedsthe operational threshold of the receiving device 120, the switch 208 isclosed and the output of the second differential amplifier 204 providesa control signal to the regulating circuit 210 relative to the desiredamount of excess power that is to be dissipated from the V_(RECT) node220 to reduce V_(RECT) in line with the operational parameters of thereceiving device 120. In an embodiment, the value of V_(REF2) may be setin about 0.5 V steps from about 2.5 V up to about 4 V. The gain of thefirst differential amplifier 202 may be set to about 0 dB. The value ofV_(REF2) and the gain of the differential amplifier may be aprogrammable value that is configurable using, for example, themicrocontroller 212.

The regulation loop circuit 240 may continue to dissipate the excesspower through the regulating circuit 210, to provide sufficient time forthe receiving device 120 to communicate a clear signal 150 to thetransmitting device 110 and request a reduction of the transfer power140.

Advantageously, the embodiments of this disclosure allow the receivingdevice 120 to use in-band communication to communicate with thetransmitting device 110 without the packet corruption that may occur asa result of, for example, with detuning or a hard over-voltageprotection method.

Additionally, the regulation loop circuit 240 is advantageously capableof effectively clamping at any programmable voltage. This is in contrastto the clamping operation using Zener diodes, which is rigid and notconfigurable.

Furthermore, the effective clamping process in the embodiments of thisdisclosure is an active process. Thus, the regulation loop circuit 240is able to release the clamping at any time, which again is differentfrom a clamping operation using Zener diodes.

In some embodiments, the activation of switch 208 may trigger a signalto be received at the microcontroller 212. In turn, the microcontrollermay provide a packet to be transmitted to the transmitting device 110 torequest a reduction in, or to end, the power transfer.

It should be noted that some excess power may be dissipated at thevoltage regulator 130 due to the range of input voltages at which thevoltage regulator 130 is capable of providing a stable output voltage tothe load 132.

In an exemplary embodiment, the steady-state value of V_(OUT) is 20 V,the gain of the first differential amplifier 202 and the seconddifferential amplifier 204 is 0 dB, the value of V_(REF2) is set to 4 V,and the value of V_(REF1) is set to 2 V. In a first scenario of thisexemplary embodiment, and in proper operational mode, V_(RECT) is at 20V and the output of the first differential amplifier 202 is near 0 V. Asthe output of the first differential amplifier 202 is less than 4 V, theswitch 208 remains open, the regulating circuit 210 is inactive, andV_(RECT) remains at 20V.

In a second scenario of the above exemplary embodiment, V_(RECT) exceeds24 V and the output of the first differential amplifier 202 is nowgreater than 4 V. As the output of the first differential amplifier 202exceeds 4 V, the switch 208 is now closed. The second differentialamplifier 204 provides a control signal to the regulating circuit 210such that V_(RECT) remains at about 24 V. The regulating circuit 210dissipates a corresponding amount of power from the V_(RECT) node 220,which stabilizes the value of V_(RECT).

In an embodiment, the rectifier 126, the voltage regulator 130, themicrocontroller 212, the differential amplifiers 202 and 204, thecomparator 206, and the switch 208 may be formed in an integratedcircuit (IC). Optionally, the integrated circuit may have additionalcomponents (not shown), such as a memory, a clock generator, a thermalprotection circuit, an analog-to-digital converter (ADC), or the like.The memory may store an operating system, communication or configurationinstructions. The clock generator may generate a clock signal tosynchronize operations within the integrated circuit or the receivingdevice. The thermal protection circuit may be used to monitor, andprotect against, over-heating conditions in the integrated circuit.

The integrated circuit may provide a highly efficient and low-powerdissipating packaged circuit capable of integration in compactapplications. The integrated circuit may have a plurality of terminalsto connect to external discrete components, such as capacitors,resistors, inductors, or windings. In an embodiment, the integrated maybe packaged in a flip-chip configuration. The integrated circuit mayhave terminals to interconnect the output of the switch 208 to theregulating circuit 210 and to conditionally provide the voltageV_(CONT). The integrated circuit may support a variety of standard orproprietary standards, such as the single wire protocol (SWP) interface,the serial peripheral interface (SPI), and the inter-integrated circuit(I2C) interface.

The IC provides a highly efficient and low-power dissipating circuitthat is capable of integration in compact applications. The IC maycomply with one or more wireless standard communication protocols, suchas the Qi or AirFuel standards. The thermal protection circuit maydetect that one or more of the components in the receiving device haveexceeded a thermal threshold and trigger a signal to the microcontroller212. The microcontroller 212, in response to receiving the trigger fromthe thermal protection circuit, and any other trigger, for example fromthe switch 308, may transmit a packet to the transmitting device toreduce, or end, the power transfer.

FIG. 3 is a schematic diagram of an embodiment wireless power system 300having a regulation loop circuit 310. The regulation loop circuit 310,similar to the regulation loop circuit 240, provides protection againstover-voltage conditions at the load or receiving elements of thereceiving device 120. However, switch 208 in the regulation loop circuit310 is activated in response to a trigger from the multiplexer 306 basedon any configured combinational logic of a) the difference between thevoltages V_(RECT) and Vou, b) the difference between the voltagesV_(RECT) and a first threshold (V_(TH1)), and c) the difference betweenthe voltages V_(OUT) and a second threshold (V_(TH2)).

The regulation loop circuit 310, in addition to the componentspreviously discussed in FIG. 2 , includes two additional comparators 302and 304 and a multiplexer 306, which may (or may not) be arranged asshown in FIG. 3 . The receiving device 120 and the transmitting device110 may include additional components not depicted in FIG. 3 , such aslong-term storage (e.g., non-volatile memory, etc.) or a non-transitorycomputer-readable medium. The regulation loop circuit 240 includes a 1)monitoring circuit, comprising the differential amplifiers 202 and 204,the comparators 206, 302, and 304, the multiplexer 306, and the switch208, and 2) the regulating circuit 210.

Comparators 302 and 304 are functionally similar to comparator 206 ofFIG. 2 . A first (i.e., positive-side) input of the comparator 302 iscoupled to V_(RECT) node 220. A second (i.e., negative-side) input ofthe comparator 302 is coupled to V_(TH1). A first (i.e., positive-side)input of the comparator 304 is coupled to V_(OUT) node 230. A second(i.e., negative-side) input of the comparator 304 is coupled to V_(TH2).It should be noted that in some embodiments, the input voltages at thepositive side and the negative side of comparators 302 and 304 may beswapped. The values of the threshold voltages V_(TH1) and V_(TH2) areselected, respectively, in accordance with the steady-state operationalmode values at the V_(RECT) node 220 and the V_(OUT) node 230. In anembodiment, the values V_(TH1) and V_(TH2) may be programmable throughthe microcontroller 212 and set from 23 V up to 26.5 V, in 0.5 Vincrements.

The multiplexer 306 is coupled to the output of each comparator 206,302, and 304. The multiplexer 306 receives an output signal from eachcomparator 206, 302, and 304, and provides an activation signal toswitch 208. Therefore, the multiplexer 306 may be configured to providean activation signal to switch 208 based on the voltage V_(RECT)exceeding V_(OUT) by a value greater than V_(REF2), the voltage V_(RECT)exceeding V_(TH1), the voltage V_(OUT) exceeding V_(TH2), or acombination thereof. The regulation loop circuit 310 advantageouslyprovides over-voltage monitoring by directly monitoring the voltagesV_(RECT) and V_(OUT) in addition to monitoring the voltage differencebetween V_(RECT) and V_(OUT).

The multiplexer 306 may be configured using the microcontroller 212. Themicrocontroller 212 may include a memory component that stores variousconfiguration settings. The various configuration settings may beselected such that the multiplexer 306 provides a trigger to activateswitch 208 based on any logical combination of signals received from thecomparators 206, 302, and 304. The various configuration settings may bepre-programmed at the multiplexer or programmed through, for example, afirmware update.

In an exemplary embodiment, the steady-state value of V_(OUT) is about20V, the gain of the first differential amplifier 202 is about 0 dB andthe second differential amplifier 204 is 20 dB, the value of V_(REF2) isset to about 4V, the value of V_(REF1) is set to about 4V, and thevalues of V_(TH1) and V_(TH2) are set to about 24 V. In a first scenarioof this exemplary embodiment, and in proper operational mode, V_(RECT)is at about 20V and the output of the first differential amplifier 202is near 0 V. The output of comparators 206, 302, and 304 remains low.The output of the multiplexer 306 remains low and the switch 208 remainsopen, the regulating circuit 210 is inactive, and V_(RECT) remains atabout 20V.

In a second scenario of the above exemplary embodiment, V_(RECT) exceeds24V. The output of the first differential amplifier 202 is greater than4 V. The output of the comparators 206, 302, and 304 are high and switch208 is closed. The second differential amplifier 204 provides a controlsignal to the regulating circuit 210. The regulating circuit 210 isenabled and dissipates a corresponding amount of power from V_(RECT),which reduces the value of V_(RECT).

This solution advantageously provides a reliable and multi-angledapproach to the monitoring of an over-voltage condition in the receivingdevice 120. This solution may counteract a situation at which VOUT andVRECT may experience an uncorrelated behavior and the regulation loopcircuit is configured to properly activate.

In an embodiment, the rectifier 126, the voltage regulator 130, themicrocontroller 212, the differential amplifiers 202 and 204, thecomparators 206, 302, and 304, the multiplexer 306, and the switch 208may be formed in an integrated circuit (IC). Optionally, the integratedcircuit may have additional components (not shown), such as a memory, aclock generator, a thermal protection circuit, an analog-to-digitalconverter (ADC), or the like. The integrated circuit may have terminalsto interconnect with the regulating circuit 210 and to conditionallyprovide the voltage V_(CONT). The integrated circuit may have aplurality of terminals to connect to external discrete components, suchas capacitors, resistors, inductors, or windings. In an embodiment, theintegrated may be packaged in a flip-chip configuration. The integratedcircuit may have terminals to interconnect the output of switch 208 tothe regulating circuit 210 and to conditionally provide the voltageV_(CONT).

FIG. 4 is a schematic of an embodiment regulating circuit 210 for awireless power system. The regulating circuit 210 includes an activedevice 410 and a dissipating element 420. The active device 410 receivesa voltage V_(CONT) when switch 208 is activated. The value of V_(CONT)is set such that the active device 410 has only enough conductivity todissipate a specific amount of excess energy from V_(RECT) and to setthe voltage at the V_(RECT) node 220 to normal operating conditions. Theexcess energy is dissipated through the dissipating element 420 toreference ground at the V_(REF) node 160 and additionally through thevoltage regulator 130.

The active device 410 has an input terminal 412, an output terminal 414,and a control terminal 416. The input terminal 412 is coupled to theV_(RECT) node 220, the output terminal 414 is coupled to the dissipatingelement 420, and the control terminal 416 is coupled to the V_(CONT)node 250. In an embodiment, the active device 410 is a MOSFET. In someembodiments, the active device 410 may be a set of active devices.

The active device 410 is controlled through the voltage V_(CONT) at thecontrol terminal 416. The active device 410 operates linearly and theconductivity of the active device 410 depends on the value of thevoltage V_(CONT). The voltage V_(CONT) is provided from the seconddifferential amplifier 204, as shown, for example, in the wireless powersystem 200 of FIG. 2 .

In some embodiments, the dissipating element 420 may include one or moreadditional active devices. Optionally, in such embodiments, a sourceresistor may be coupled between the active device 410 and the one ormore additional active devices to provide a smooth crossover between theactive devices. As an example, the dissipating element 420 may include asilicon-controlled rectifier (SCR) or other similar types ofsemiconductor devices.

In some embodiments, the dissipating element 420 may be formed as one ormore discrete components. In other embodiments, the dissipating element420 may be formed in one or more integrated circuits (ICs). In oneembodiment, the dissipating element 420 includes one or more resistors.

The active device 410 is biased such that as the active device 410becomes conductive, the dissipating element 420 begins to sink currentto ground. The value of the voltage V_(CONT) is set such that only asmuch current as is necessary is sunk to ground to provide a regulatedvoltage at the V_(RECT) node 220.

When the wireless power system is operating at a steady-state mode(e.g., V_(RECT) is close to V_(OUT)), the value of the voltage V_(CONT)is set such that the active device 410 is not conducting and theregulating circuit 210 is not dissipating any current through thedissipating element 420.

FIGS. 5A-C are plots of embodiment operational timing diagrams, as maybe performed by a receiving device in accordance with the embodiments ofthis disclosure. In each timing diagram, at time T₀, an event occurswhere the output power of the transmitting device begins to exceed thesteady-state operational voltage of the receiving device. At time T₁,the difference in value between the two voltages V_(RECT) and V_(OUT)exceeds the voltage V_(REF2) (see plot 502), at which time the switch208 is activated and the voltage V_(CONT) is provided to the regulatingcircuit 210 (see plot 504).

FIG. 5A is a plot of an embodiment operational timing diagram 500 in afirst operational scenario. In the first operational scenario, thereceiving device 120 at time T₂, shortly after the activation of theswitch 208 and the activation of the regulating circuit 210 at time T₁,transmits an end power transfer (EPT) request to the transmitting device(see plot 506). Between time T₂ and time T₃, the transmitting devicereceives the EPT request and the power transmission is successfullyhalted. In response, at time T₃, the difference in value between thevoltages V_(RECT) and V_(OUT) falls below V_(REF2) (see plot 502), atwhich time the switch 208 is deactivated and the voltage V_(CONT) is nolonger provided to the regulating circuit 210 (see plot 504). Shortlythereafter, at time T₄, the receiving device stops the EPT requesttransmission (see plot 506).

FIG. 5B is a plot of an embodiment operational timing diagram 520 in asecond operational scenario. In the second operational scenario, thereceiving device 120 at time T₂, shortly after the activation of theswitch 208 and the activation of the regulating circuit 210 at time T₁(see plot 522), transmits an end power transfer (EPT) request to thetransmitting device (see plot 526). However, unlike the firstoperational scenario, the EPT request is unsuccessful and the powertransmission is not halted (see plot 526).

The switch 208 remains activated and the voltage V_(CONT) continues tobe provided to the regulating circuit 210. Until at time T₅, at whichtime the switch 208 is deactivated and the amplified difference in valuebetween the two voltages V_(RECT) and V_(OUT) begins to increase (seeplot 522). Until at time T₆ when, for example, a more drastic protectionscheme like hard over-voltage protection is applied at the receivingdevice 120 (see plot 528). This results in the shutting down of thereceiving device at risk of deterioration of the receiving device and/orthe transmitting device, but that may be used as an ultimatecountermeasure. The time period between time T₅ and time T₁ may be setas a configurable (i.e., programmable) option using the microcontroller212 or a similar component. In some embodiments, the time period may beset anywhere from as little as 50 milliseconds (ms), up to 300 ms.

The wireless power system advantageously allows for the system to returnto steady-state mode within the time period T₁ and T₅. If the wirelesspower system, however, does not return to steady-state mode (i.e., theoriginal steady-state mode before the surge of incoming power) withinthat period of time, the hard over-voltage protection is applied at timeT₆, to protect the wireless power system from further damage. Thedifference in time between time T₆ and T₁, or time T₆ and T₅, may be aconfigurable option.

FIG. 5C is a plot of an embodiment operational timing diagram 540 in athird operational scenario. In the third operational scenario, thereceiving device waits until time T′₂ to transmit the end power transfer(EPT) request to the transmitting device (see plot 544). The delay,advantageously allows the wireless power system to remain operational inthe event that a surge in power occurs for a short period of time (i.e.,less than T′₂-T₁). For instance, if the surge in power occurs for aperiod of time that is less than the delay, the receiving device doesnot send the EPT request. The delay may be a configurable option usingthe microcontroller 212. In some embodiments, the delay may be fromabout 1 microseconds (μs) to about 10 μs.

FIG. 6 is a schematic diagram of an embodiment wireless power system 600having a current sensing element 602. The wireless power system 600,similar to the wireless power systems 200 and 300, provides over-voltageprotection at the load and receiving elements of the receiving device120. The wireless power system 600, in additional to the componentspreviously disclosed in FIG. 2 , includes the current sensing element602, which may (or may not) be arranged as shown. As shown, the currentsensing element 602 is a resistor. However, other components may becontemplated to serve a similar function.

The current sensing element 602 is coupled in series between the outputof the rectifier 126 and the input of the voltage regulator 130. Theinput node of the regulating circuit 210 is coupled between the outputof the rectifier 126 and the current sensing element 602.

A current-sensing amplifier, for example in the microcontroller 212, canbe used to monitor and accurately measure the voltages across thecurrent sensing element 602 and the power at the receiving device 120.The receiving device 120 may communicate the level of power at thecurrent sensing element 602 to the transmitting device 110, for example,in response to a foreign objection detection (FOD) check by thetransmitting device 110.

In one embodiment, the transmitting device 110 can compare the powerreceived at the receiving device with the power being transmitted. Thetransmitting device 110 may then determine that a power loss conditionhas occurred at the receiving device 120 to shut down the powertransfer.

Indeed, as the regulating loop circuit 240—and in particular, theregulating circuit 210—is placed before the current sensing element, anypower absorbed by the regulating circuit 210 is not taken into accountin the power reported by the microcontroller 212. Thus, in the eventthat the microcontroller 214 of the transmitting device 110 prompts thereceiving device 120 to report power, and make a comparison, themicrocontroller 214 may resolve that some power is lost at the receivingdevice 120 and determine that a foreign object device (FOD) condition ispresent.

FIG. 7A is a schematic diagram of a receiving device 700 configured withZener diodes (i.e., Z1 702, Z2 704, Z3 706, and Z4 708) in a clampingcircuit. The clamping circuit, or limiter, is used to limit or cut-offportions of the incoming voltage at the rectifier 126. The values of theZener diodes Z1 702, Z2 704, Z3 706, and Z4 are selected such as to clipan AC voltage that exceeds a threshold voltage at the rectifier 126.This effectively regulates the incoming AC voltage at the rectifier 126.

As shown, Zener diode Z1 702 and Zener diode Z2 704 are arranged asback-to-back connected Zener diodes. The cathode terminal of Z1 702 iscoupled to the first terminal of the second windings 122 through theresonant capacitor 124. The anode terminal of Z 702 is connected to theanode terminal of Z2 704. The cathode terminal of Z2 is connected toreference ground. The Zener diodes Z3 706 and Z4 708 are also arrangedas back-to-back connected Zener diodes. The cathode terminal of Z3 706is connected to the second terminal of the second windings 122. Theanode terminal of Z3 706 is connected to the anode terminal of Z4 708.The cathode terminal of Z8 is connected to reference ground.

Although the solution is functional, the receiving device 700 is unawarethat the clipping has occurred and that the voltage from a transmittingdevice exceeds the operational limits of the receiving device 700.Therefore, disadvantageously the receiving device 700 does notcommunicate a request to reduce the power level to the transmittingdevice. The solution is purely a safety precaution and disadvantageouslydoes not provide a corrective action. Furthermore, excess power iscontinuously being dissipated through the receiving device 700, whichmay damage one or both of the receiving device 700 and the transmittingdevice. Also, the voltage clamping at the output of the rectifier 126 isfixed in voltage in respect to the reference. This may not adequatelyaddress various over-voltage scenarios, especially if the voltage at theoutput of the voltage regulator 130 is programmable. This may lead to alarge range of operating voltage at the output of the rectifiers 126.

FIG. 7B is a schematic diagram of a receiving device 750 configured witha de-tuning circuit. The de-tuning circuit includes a pair of activedevices 752 and 756 and a pair of capacitors 754 and 758. Each capacitor754 and 758 is coupled to an input terminal of the rectifier 126. Theactive device 752 is activated in accordance with the control signal 760and the active device 756 is activated in accordance with the controlsignal 762. The control signals 760 and 762 may be provided by amicrocontroller or activated automatically, for example, through aregulating monitoring circuit.

The receiving device 750, in response to determining an excess ACvoltage at the input of the rectifier 126, provides control signals 760and 762 to the active devices 752 and 756. The capacitors 754 and 758de-tune the impedance between the second windings 122 and the rectifier126. This effectively reduces the resonance factor at the secondwindings 122.

Similar to FIG. 7A, this is a functional solution to reduce the voltageat the rectifier 126. The level of de-tuning, however, is limited andcan only protect the receiving device 750 against a limited amount ofexcess power. Therefore, disadvantageously the voltage at the input ofthe voltage regulator 130 may continue to increase despite theactivation of the soft over-voltage-protection provided by thede-tuning.

FIG. 7C is a schematic diagram of a receiving device 780 configured witha hard over-voltage protection circuit. The hard over-voltage protectioncircuit may be implemented in any of the embodiments of this disclosure.

The hard over-voltage protection circuit includes a first active device782 and second active device 784. The first active device 782 is coupledbetween a first input terminal 786 of the rectifier 126 and referenceground. The second active device 784 is coupled between a second inputterminal 788 of the rectifier 126 and reference ground. In anembodiment, each of the first and second active device 782 and 784 is aMOSFET.

When the AC voltage at the two input terminals 786 and 788 of therectifier 126 exceeds a predetermined voltage, the hard over-voltageprotection may kick in. The hard over-voltage protection consists ofshorting each of the two input terminals 786 and 788 to the referenceground through activating the first and second active device 782 and784, respectively.

Disadvantageously, the solution blocks incoming wireless power transfer.Therefore, the receiving device 780 may not be able to properlycommunicate with the transmitting device 110, specifically in the caseof in-band communication. Additionally, the excess power is dissipatedin a limited number of components, which can cause damage to the variouscomponents.

These and other issues of the prior art are addressed with theembodiments of this disclosure, for example using the embodiments inFIGS. 2-4 .

FIG. 8 is a flowchart of an embodiment method 800 for monitoring anover-voltage condition and regulating the input voltage to a voltageregulator 130 using a regulating circuit, as may be performed by areceiving device. At step 810, the receiving device monitors the voltageacross the input and output terminals of the voltage regulator 130 usinga monitoring circuit. In some embodiments, the monitoring may includedirect voltage monitoring at each terminal. In some embodiments, themonitoring may include a difference in voltage across the voltageregulator 130. In other embodiments, the monitoring may include directvoltage monitoring at each terminal and monitoring the difference involtage across the voltage regulator 130.

At step 820, the monitoring circuit upon determining that anover-voltage condition is present at the receiving device, activates aregulating circuit 210. The regulating circuit 210 regulates the voltageat the output of the rectifier 126 to return the voltage to asteady-state value. In one embodiment, the monitoring circuit maydetermine the over-voltage condition after detecting that the voltageV_(RECT) exceeds a threshold voltage V_(TH1). In one embodiment, themonitoring circuit may determine the over-voltage condition afterdetecting that the voltage V_(OUT) exceeds a threshold voltage V_(TH2).In one embodiment, the monitoring circuit may determine the over-voltagecondition after detecting that the difference in voltage between thevoltage V_(RECT) and V_(OUT) exceeds a reference voltage V_(REF2). Inother embodiments, the monitoring circuit may determine the over-voltagecondition after detecting any logical combination of any of the previousconditions.

The regulating circuit receives a voltage V_(CONT) from the monitoringcircuit. The value of V_(CONT) is set such that the regulating circuit210 reduces the value of the voltage V_(RECT) to a value near thesteady-state voltage. In practical terms, the wireless power systemreaches a new steady-state mode in which the value of the V_(RECT)voltage is higher than the former steady-state mode (i.e., steady-statemode before the incoming power surge). The new steady-state mode isstill within the steady-state parameters for which voltage is determinedby the wireless power system parameters.

Optionally, at step 830, the receiving device may communicate to thetransmitting device an end power transfer (EPT) request. In someembodiments, the EPT request is transmitted immediately after step 820and the activation of the regulating circuit 210. In other embodiments,the transmission of the EPT request is delayed until a period of timehas elapsed. In these embodiments, the receiving device checks if theregulating circuit 210 is still activated after the delay period, beforetransmitting the EPT request.

Optionally, at step 840, the receiving device may activate hardover-voltage protection and stop the receiving of the power at thereceiving device. The receiving device may delay the activation of thehard over-voltage protection for a period of time after the regulatingcircuit 210 is activated to allow for the EPT request to be received andthe transmitting device to shut down the power transfer.

It is noted that the receiving device 120 in the various embodiments ofthis disclosure may additionally include over-current, over-voltage, andover-temperature sensing circuits. The various sensing circuits may workin combination with the regulation loop circuit in the variousembodiments to provide additional safety protection to the receivingdevice 120.

Although the description has been described in detail, it should beunderstood that various changes, substitutions, and alterations may bemade without departing from the spirit and scope of this disclosure asdefined by the appended claims. The same elements are designated withthe same reference numbers in the various figures. Moreover, the scopeof the disclosure is not intended to be limited to the particularembodiments described herein, as one of ordinary skill in the art willreadily appreciate from this disclosure that processes, machines,manufacture, compositions of matter, means, methods, or steps, presentlyexisting or later to be developed, may perform substantially the samefunction or achieve substantially the same result as the correspondingembodiments described herein. Accordingly, the appended claims areintended to include within their scope such processes, machines,manufacture, compositions of matter, means, methods, or steps.Regardless of the standard or type of wireless power transfer used,embodiments of this disclosure provide solutions to address over-voltageat the receiving elements and/or loading elements of the receivingdevice.

The specification and drawings are, accordingly, to be regarded simplyas an illustration of the disclosure as defined by the appended claims,and are contemplated to cover any and all modifications, variations,combinations, or equivalents that fall within the scope of the presentdisclosure.

What is claimed is:
 1. A method for regulating an over-voltage conditionin a wireless power system, the method comprising: receiving, by areceiving device of the wireless power system, an alternating currentvoltage; converting the alternating current voltage to a direct currentvoltage; converting the direct current voltage to a first regulateddirect current voltage; determining that the alternating current voltageexceeds a steady-state operating condition and, based thereon,converting the direct current voltage to a second regulated directcurrent voltage; measuring a voltage value of the direct current voltageacross a sense resistor; calculating a power value received at thereceiving device at the sense resistor; and communicating the powervalue received to a transmitting device of the wireless power system. 2.The method of claim 1, wherein the determining that the alternatingcurrent voltage exceeds the steady-state operating condition comprisesdetermining that a difference between the direct current voltage and thefirst regulated direct current voltage exceeds a first threshold.
 3. Themethod of claim 1, wherein the determining that the alternating currentvoltage exceeds the steady-state operating condition comprisesdetermining that a difference between the direct current voltage and thefirst regulated direct current voltage exceeds a first threshold, thedirect current voltage exceeds a second threshold, the first regulateddirect current voltage exceeds a third threshold, or a combinationthereof.
 4. The method of claim 3, wherein the receiving devicecomprises a plurality of differential amplifiers, and wherein thedetermining that the difference between the direct current voltage andthe first regulated direct current voltage exceeds the first thresholdis determined by a first differential amplifier, the determining thatthe direct current voltage exceeds the second threshold is determined bya second differential amplifier, and the determining that the firstregulated direct current voltage exceeds the third threshold isdetermined by a third differential amplifier.
 5. The method of claim 1,wherein the determining that the alternating current voltage exceeds thesteady-state operating condition is based on a combinational logic of avalue of the direct current voltage, the first regulated direct currentvoltage, and a difference between the direct current voltage and thefirst regulated direct current voltage.
 6. The method of claim 1,wherein the receiving device comprises a monitoring circuit having afirst differential amplifier, a second differential amplifier, acomparator, and a switch, and wherein the determining that thealternating current voltage exceeds the steady-state operating conditioncomprises the determining by the monitoring circuit.
 7. The method ofclaim 1, wherein the determining that the alternating current voltageexceeds a steady-state operating condition comprises determining that adifference between the direct current voltage and the first regulateddirect current voltage exceeds a first threshold, wherein the convertingis based on determining that the alternating current voltage exceeds thesteady-state operating condition, and wherein the determining that thedifference between the direct current voltage and the first regulateddirect current voltage exceeds the first threshold is determined by afirst differential amplifier.
 8. A method for regulating an over-voltagecondition in a receiving device of a wireless power system, the methodcomprising: converting an alternating current voltage received from atransmitting device of the wireless power system to a direct currentvoltage; converting the direct current voltage to a first regulateddirect current voltage; determining that the alternating current voltageexceeds a steady-state operating condition comprising determining that adifference between the direct current voltage and the first regulateddirect current voltage exceeds a first threshold and, based thereon,converting the direct current voltage to a second regulated directcurrent voltage; measuring a voltage value of the direct current voltageacross a sense resistor; calculating a power value received at thereceiving device at the sense resistor; and communicating the powervalue received to the transmitting device of the wireless power system.9. The method of claim 8, wherein the converting is based on determiningthat the alternating current voltage exceeds the steady-state operatingcondition.
 10. The method of claim 8, wherein the determining that thealternating current voltage exceeds the steady-state operating conditioncomprises determining that a difference between the direct currentvoltage and the first regulated direct current voltage exceeds the firstthreshold, the direct current voltage exceeds a second threshold, thefirst regulated direct current voltage exceeds a third threshold, or acombination thereof.
 11. The method of claim 10, wherein the receivingdevice comprises a plurality of differential amplifiers, and wherein thedetermining that the difference between the direct current voltage andthe first regulated direct current voltage exceeds the first thresholdis determined by a first differential amplifier, the determining thatthe direct current voltage exceeds the second threshold is determined bya second differential amplifier, and the determining that the firstregulated direct current voltage exceeds the third threshold isdetermined by a third differential amplifier.
 12. The method of claim 8,wherein the determining that the alternating current voltage exceeds thesteady-state operating condition is based on a combinational logic of avalue of the direct current voltage, the first regulated direct currentvoltage, and a difference between the direct current voltage and thefirst regulated direct current voltage.
 13. The method of claim 8,wherein the receiving device comprises a monitoring circuit having afirst differential amplifier, a second differential amplifier, acomparator, and a switch, and wherein the determining that thealternating current voltage exceeds the steady-state operating conditioncomprises the determining by the monitoring circuit.
 14. The method ofclaim 8, wherein the determining that the difference between the directcurrent voltage and the first regulated direct current voltage exceedsthe first threshold is determined by a first differential amplifier. 15.A receiving device of a wireless power system, the receiving devicecomprising: a rectifier configured to convert an alternating currentvoltage to a direct current voltage; a voltage regulator configured toconvert the direct current voltage to a first regulated direct currentvoltage; a sense resistor configured to measure a voltage value of thedirect current voltage; and a monitoring circuit configured to:determine that the alternating current voltage exceeds a steady-stateoperating condition based on a combinational logic of a value of thedirect current voltage, the first regulated direct current voltage, anda difference between the direct current voltage and the first regulateddirect current voltage and, based thereon, convert the direct currentvoltage to a second regulated direct current voltage, calculate a powervalue received at the receiving device at the sense resistor, andcommunicate the power value received to a transmitting device of thewireless power system.
 16. The receiving device of claim 15, wherein themonitoring circuit comprises a switch, a first differential amplifier, asecond differential amplifier, a third differential amplifier, acomparator, and a multiplexer.
 17. The receiving device of claim 15,wherein the determining that the alternating current voltage exceeds thesteady-state operating condition based on a combinational logiccomprises determining, by a first differential amplifier and acomparator, that the difference between the direct current voltage andthe first regulated direct current voltage exceeds a first threshold,determining, by a second differential amplifier, that the direct currentvoltage exceeds a second threshold, or determining, by a thirddifferential amplifier, that the first regulated direct current voltageexceeds a third threshold.
 18. The receiving device of claim 15, furthercomprising a microcontroller configured to communicate an End PowerTransfer request to stop transmitting of the alternating current voltageby the transmitting device of the wireless power system, and thecommunicating the End Power Transfer request being in response to thealternating current voltage exceeding the steady-state operatingcondition.
 19. The receiving device of claim 15, wherein communicatingthe End Power Transfer request is communicated using an in-bandcommunication path.
 20. The receiving device of claim 15, whereincommunicating the End Power Transfer request is delayed for a set lengthof time after determining the alternating current voltage exceeds thesteady-state operating condition.